The United States has designated USS Colorado (SSN 788) as the first submarine assigned to a planned rotational force in Western Australia, with operations slated to begin in late 2027, the three AUKUS partner nations announced on Monday, 26 October 2026. The Virginia-class fast-attack submarine will be stationed at HMAS Stirling, a Royal Australian Navy base, as part of the newly established Submarine Rotational Force–West (SRF-West).

Key Developments

The announcement was made jointly by US Secretary of Defense Pete Hegseth, Australian Deputy Prime Minister and Defence Minister Richard Marles, and British Defence Secretary Wes Streeting. The joint statement described the selection as 'a significant milestone for AUKUS Pillar I and a decisive step in strengthening collective deterrence in the Pacific.'

SRF-West is projected to host up to four American submarines and one British submarine at HMAS Stirling. The announcement coincides with a US submarine maintenance period beginning later this week, which the partners said would further demonstrate Australia's growing capacity to sustain American and British nuclear-powered fast-attack submarines.

What AUKUS Pillar I Means for Australia

The rotational force is central to AUKUS Pillar I — the pathway through which Australia is preparing to own, operate, maintain, and regulate a sovereign, conventionally armed, nuclear-powered submarine capability. Notably, the joint statement was explicit that the capability being developed is conventionally armed — meaning it carries no nuclear weapons — though the submarines are nuclear-powered.

The force will operate at Australia's invitation and on terms mutually agreed by the three governments. Its activities will be governed by the US–Australia Force Posture Agreement and relevant international nuclear agreements, including obligations under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and Australia's commitments under the South Pacific Nuclear Free Zone Treaty, also known as the Treaty of Rarotonga.

Infrastructure and Personnel Build-Up

Preparations for SRF-West have been under way for some time. In June 2026, Australia announced the re-establishment of US Submarine Squadron 3 to oversee American submarine rotations, alongside a dedicated maintenance organisation and Naval Support Activity Stirling. According to that announcement, more than 200 Royal Australian Navy personnel were already undertaking training and postings in the United States, while more than 220 Australian industry personnel were gaining hands-on experience at Pearl Harbour Naval Shipyard.

The partners said the rotational force would also expand maintenance options and the infrastructure needed to sustain submarine operations across the Indo-Pacific region.

About USS Colorado

USS Colorado was commissioned on 17 March 2018. It is the 15th Virginia-class submarine and the fifth built to the redesigned Block III configuration, making it among the more modern hulls in the US fleet. It is the fourth US Navy vessel to bear the name of the state of Colorado.

Political Backing and What Comes Next

The joint statement noted that US President Donald Trump, Australian Prime Minister Anthony Albanese, and British Prime Minister Andy Burnham had reaffirmed that AUKUS was moving 'full steam ahead.' The political consensus across all three governments — spanning different parties — signals that the trilateral arrangement retains bipartisan support in each country. The commencement of operations at HMAS Stirling from late 2027 will mark the first time nuclear-powered submarines have been permanently based in Australian waters, a development that analysts expect to draw close scrutiny from China and other regional powers.